Spark-plug mold



- SPARK' P Lue Molo. l

FILED DEC. I2. 19.19. 4 -SSIiEETS-S'l-IIEET l.

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Dec. 19, 1922.

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Dec. 19, 1922.

' 1,439,667. C. E. GERBAUD. SPARK PLUG MoLo.

FILED DEC. l2. |919- 4 SHEETS-SHEET /Alf/VTOK 3y/:aff 3W/z 'eaa Patented Bec. i9, 1922.`

insee? oHAnLEsEMILf-GEBBAUD, or PARIS, FRANCE.

`SPARK-15mm MOLD.

Application led December 12, 1919. v Serial No.' 344,493.

To all whomz'z may-concern: f

Be it known that I, ^i-Linnns EMIL GER- BAUD, of 102 Fue Pelleport, Faris, France,

manufacturer of glassware, have invented Improvements in Spark-Plug Molds, of" which' the following is a full, clear, and ex act description. Y

lThis invention relates to molds for use in the manufacture of glass-insulated sparkingplugs, by casting the glass insulation in the nieta-l shell of the plug. n i

@parkings plugs have already been designed in which the insulating body consists of a mass of glass cast in the shell of the plug, but the existing processes have never been able to give good results, for the reason that when the molten massis introduced 'and compressed direct in the shell, the molecules y of glass are firmly pressed against each other, and experience has shown that the result of this compression is to cause the formation, in the mass of glass, on cooling, of crack through which leakages can occur.y

The object of the present inventionis to provide a mold arranged in such a way as to enable the glass insulation to be cast Aon to the axial electrode inside the shell under such conditions that the inconvenience described cannot arise. f

According to this invention a mold is provided with a pouring gate which is offset, axially, in relation to that portion of the mold in which the glass insulation is'to be cast, and communicates `with the body ofthe.

mold by way of an opening of smaller diameter.A f

By virtue of this device the moltenglass filling the shell is relieved to a largeextent of the pressure of the column of glass inthe pouring gate, and, in addition, of the pressure exerted on said column of glass during* In some cases a plug carrier may bepmvided inside the mold, to facilitate the removal of the plug from the mold, and enable suclr removal to be effected directly after the glass has been cast, so that the mold need not be idle during vthe time the glass is n cooling, but can be used at once fory making another plug.

This plug carrier comprises a lower ring, resting on the bottom of the ymold and sup--` portingfthe shell of the plug, and a cap covering said shell, said ring and capbeing provided with handles lwhich enable them to be easily held when the plug is being taken out of themold, so that the plug. can be taken out of the mold as soon as the glass has been cast.v f

The invention is illustrated by the accomv panying drawings inv which:

Figs. l to 5 show one form of the invention," i f F igzl being a front elevation of the inside of one of the shells of the mold,

Fig. 2 being a plan of themold,

' Fig. 3 a vertical section'of the mold along the line A--A of Fig. 2, the shell` of the plug 'and the plug carrier being shewn in position inside the mold; i

Fig. et being a horizontal section, along the line-B-i-B of Fig. 3, and Fig. 5 being asec-y tional elevation of detail shewing thek core intended tokeep the electrode rod in position inside the mold. f

Fig. 6 is a vertical section of a mold for the manufacture of a plug with a spark-gap electrode.

Figs. 7 to lO shew the improved type of n'rold'vwith an internal plug carrier, Fig. 'T being-a vertical section along the lineC-C of Figure 8; Figs. Sand 9 shewing thc mold in plan, open and closed respectively; whilst Fig. lOshews the plug and the device by which itis lifted out ofthe mold.

y'lhe typeof mold represented in Figs. l

to 5, which is similar to the molds usedk for glassware, is composed of two shells a,

hinged together and provided with an inter nal cavity al, which, when the vmold Lis closed, houses the metal shell b of the plug, which has ybeen made beforehandy in the ordinary way. f f

TheV lower portion of each ofthe mold shells is provided with a second cavity a2 for the .reception of a central core c (Figs. 3

to 5) the upper surface of which is formed witha hole c1 adapted to receive the llower end of a rod CZ which is to form the axial electrode of the plug. -The upper end of this rod is received in a recess a provided in each of the mold shells a.

The upper portion of the mold shells is' provided with a pouring gate e, which is ofi'-v set, axially, in relation to the internal cavity of the mold as formed by the recesses al and p housing the plug shell Z9, said gate communicating with said internal cavity by means of an opening el of small diameter.

Before the glass is poured, the plug shell.-

Fig. 3, inside the mold, and the latter closed,`

molten glass or preferablyy a good sodium silicate, is poured into the gate e; and pressure is then exerted on the surface of said.

glass, either by means of a tamping tool g, i piston or any other device. Under this pressure the molten glass passes through the small opening e? and ills the plug shell 'in such a way that a part of the upper p0rv tion of the internal cavities a? of the mold :emains empty above the plug` shell.

ln consequence cof-the axially otl'setv arrangement of the pouring gate c and the small section of the opening el only a small part of the pressure exerted on the glass is transmitted to the glass introduced into the plug shell andunder these conditions this glass is not subjected to any harmful pressure.

The glass 'thus poured into the shell l) adheres, in cooling, to the inner surface of the latter and to the electrode rod al, and under these conditions, binds these two together" completely and makes the plug perfectly tight, whatever may be vthe degree of compression of the gases inside the engine on which the said plug is mounted. Moreover, this glass by reason of its perfect homo- `geneity, is capable of withstanding rall eX-y pansion stresses.

lt should also be stated that this arrangement of the mold ensures the electrode being perfectly cent1-wed in relation to the plug shell.

Fig. (l shows the application of the improved mold to the manufacture of a sparling plug, the-electrode rod of which is provided with a spark gap. In this case the axial electrode is composed of two lengths of yrod (Z1 and d2, which, when the electrode is assembled inside the mold, are connected together by an insulating sleeve b, of glass for example, which holds these two lengths of rod in accurate position opposite each other at the desired distance apart.

Figs. 7 to lOillustra-te another form of the improved mold, provided with an internal plug carrier.

In this modiiication the two shells a of the mold are pivoted about a shaft i, mounted on a plate supported by two pillars 7c upstanding from a base plato Z. A projc`ction jl on the plate j supports a movable ring ffwprovided with handle m1. In this ring lits the lower cylindrical portion of the metal shell Z) ofthe plug in which the glass insulation is to be cast.

'Theplate y' is provided with a threaded central bore, traversed by a rod a adapted to' support the axial electrode al of the plug. This rod mythe lower end of which is provided with a handle or hand wheel 0, is threadedfat al to vscrew into the threaded bore of the plate f; and at its upper end has an axialrecess in which the electrode rod l of the plug rests freely.

i ,nt the upper part of the shell Z) a cap y) is auolied said can bein(Y furnished with a ll a 1 :a

handle p1 and formed with a .filling aperture n p2 adapted to communicate with the pouring gate e offset axially, .as above mentioned, relatively to the shell b in which the glass insulation is to be cast. Thejcap p is also formed with a central aperture adapted to receive the axial electrode d.

The rod n is also providedwith a shoulder which, when the rod is moved upward by screwing it into the plate j of the mold, comes in contact with theedge of the lower cylindrical portion of the plug shell thus lifting the plug and its cap y) and causing the latter to bear against the upper portion of the cavity provided in each of the shells ofy theniold. Moreover, by this means, the electrode rod d carried by the rod fn, is adjusted at the proper height inside the plug shell b. l i

A piston g1, adapted to force the molten glass into the plug shell, is slidable in the pouring gate c.

The plug shell Z) into which the insulating glass is to be poured is thus held in position inside the mold by the lower ring m and the cap y).

A. already stated, the plug shell 7) and the electrode rod l are heated by any means whatsoever, before theglass is poured.

lVhen the pouring is effected pressure is exerted by the piston rr/1 on the mass of glass contained in the c and when the pour ing has been completed, the mold is opened and the rod n is unscrewed so as to release it from the axial electrode l and the ring m. Then, by taking hold of the handles m1, p1, the plug supported between the ring fm, and the cap p-as shewn in Fig. lO-is lifted out of the mold. v

The plug shell Z) being closed at the upper end by the cap p, the mass of glass enclosed in it cannot suffer any deformation during the removal from the mold, so that this operation can be performed while the glass is still in a plastic state. It is therefore no longer necessary to wait until the plug has cooled down completely before proceeding to detach it from the mold, and

lll)

consequently the mold can be used for malring another plug immediately after the glass insulation has been poured.

Claims: l

1. A mold for `the manufacture of spark plugs for internal combustion engines having two chill mold sections articulated between each other analogous to the chill mold sections used inthe manufacture of glass, said mold sections each being provided with cooperating cavities, one in each mold section, and placed in such a manner to form an inside pocket within the mold sections for receiving the lower part of a spark plug shell in which the glass insulator is to be cast, two other cooperating cavities, one in each mold section loc-ated out of the axis of the first-mentioned cavities, two narrow grooves respectively on each of t-he chill mold sections cooperating to provide a restricted communication between the first and second mentioned cavities, two other cavities one in each mold section cooperating to receive an electrode bearer, said cavities opening through the bottom of the mold sections, an electrode bearer located in and forming a seal to close the lower end of the last mentioned cavities, said electrode bearer having a reduced upper end of a shape to project into and neatly it the lower hollow end of the spark plug shell and provided with a central aperture for receiving the lower end of the usual central electrode, the two chill mold sections being provided with cooperating seats opening into the upper' end of the irst mentioned cavity to receive the other end of the electrode. v

2. A mold for the manufacture of glassinsulated sparkings plugs for internal combustion engines, comprising: two hinged mold shells, similar to those of the molds used for glassware and having internal cavities adapted to house the shell of the plug into which the glass-insulation is to be poured; a plate on which are mounted these two shells; an internal electrode-carrying core on which is mounted the axial electrode; a pouring gate constituted by cavities provided in the two shells of the mold and having a common axis, when the mold is closed, axially offset in relation to the portion of the mold in which the glass-insulation is to be cast; an opening of small diameter putting the pouring gate in communication with the interior of the mold; a lower ring resting on the mold plate `and serving to support the plug shell, the said ring being provided with a handle; a cap covering the saidA plug shell arranged on this ring, the said cap being provided with a handle; an opening in this cap for pouring the glass contained in the axially offset pouring gate.

3. A mold for the manufacture of glassinsulated sparking plugs for internal combustion engines, comprising: two hinged mold shells, similar to those of t-he molds used for glassware, and having internal cavities adapted to house the shell of the plug into which the glass-insulation is to be poured; a plate on which are mounted these two shells; an electrode-carrying core screwed in the plate of the mold; a shoulder on this core, so arranged as to raise, during its upward movement produced by its screwing in the mold plate, the plug shell and against the upper part of the cavity proy vided in each of the mold shells; a pouring gate constituted by cavities provided in the two shells of the mold and having a coininon axis, when the mold is closed, axially offset in relation to the portion of the mold in which the glass-insulation is to be cast; an opening of small diameter putting the pouring gate in communication with the interior of the mold; a lower ring resting on the mold plate and serving to support the plug shell, the said ring being provided with a handle; a cap covering the said plug shell arranged on this ring, the said cap being provided with a handle; an opening in this cap for pouring the glass contained in the axially offset pouring gate.

The foregoing specification of my lmprovements in molds for the manufacture of glass-insulated sparkingplugs for internal combustion enginesr signed by me this 21st day of November 1919.

CHARLES EMIL GERBAUD. 

